A common spin-on type of filter cartridge has an outer cylindrical canister or housing enclosing a tubular filter element. One end of the housing has a tap plate with a threaded central opening to allow the filter element to be spun-on to a threaded spud on a base or head member. The spud has a central fluid passage to provide a first fluid path to the central cavity of the filter element. Other through-holes in the tap plate provide a separate fluid path from the base to the outer periphery of the filter element. An annular seal surrounding the central opening and located between the tap plate and the upper end cap separates the central fluid path from the peripheral fluid path. The filter element can be designed to filter fluid passing radially inward or radially outward through the filter element.
Such a spin-on type of filter cartridge as described above has received widespread acceptance for providing an end user with a filter cartridge which can be easily attached to and removed from a base member, and which provides satisfactory results in filtering fluid in the fluid system. Such cartridges are commonly used with internal combustion engines to filter fuel passing through the engine.
While the above-described type of spin-on filter cartridge is typically disposable, spin-on filter cartridges have also been developed where the housing is formed in two pieces and can be separated to allow removal and replacement of a spent filter element. The filter element can thereby be disposed when spent, and a fresh element introduced between the housing portions without having to dispose of the entire cartridge. This has some benefits as the disposed material is reduced, and the housing portions and other components can be manufactured from stronger and longer-lasting material (such as metal), which may not be as appropriate for disposal.
Filtering requirements, of course, can vary depending on the requirements of the fluid system. Filter elements which are suitable for replacement in an internal combustion engine, for example, commonly vary as to capacity and filter media qualities. While lower capacity and lower quality filter elements generally reduce the cost of the element for the end user, the lower cost units may not be compatible with the requirements for the engine. Incompatible or substandard replacement filter elements can have serious consequences for the operation and useful life of the engine. Moreover, the absence of a filter element within the housing can also seriously affect the life of the engine.
Certain techniques for securing a filter element to a base are shown in U.S. Pat. Nos. 5,035,797 and 5,186,829, where axially-extending keys are formed in the base of the assembly which are received in corresponding slots formed in the end cap of a filter element. The keys interlock in the slots to mount the element at a fixed angle relative to the base. The '829 patent further shows radially-projecting protrusions formed around the end cap which are received within corresponding tracks in the filter element base. A threaded locking ring retains the filter element to the base and can be removed to allow removal and replacement of the filter element. These patents generally address the problem of incompatible, substandard or missing replacement elements by requiring certain structural features to be provided on the filter element in order to match corresponding features on the base. By controlling the filter elements with such features, it can be assured that quality and capacity standards are maintained.
While these patents address some of the concerns associated with replacement filter elements, the elements shown in these patents combine the filter media with at least a portion of the housing as an integral unit, which requires these components to be thrown away when the filter element is replaced. Only a base or cover portion of the housing is retained when the filter element is replaced. This can increase the replacement cost of the element, and still have the drawback of increasing the disposal waste in landfills.
Thus, it is believed that there is a demand in the industry for a filter cartridge which prevents the use of improper, inappropriate or missing replacement filter elements, and which reduces or minimizes the waste associated with disposing of a spent filter element.